Intraocular lenses are frequently surgically implanted in the eye to replace the natural lens that has been removed. The removal of the natural lens is a typical surgical procedure to repair a cataract.
A typical intraocular lens has a magnifying optical section usually made of polymethylmethacrylate (PMMA) to which is attached retention loops or other structure for securing the optical section to the eye. One common procedure is to implant the optical section in the anterior section immediately in front of the iris. A plurality of retention loops are secured to a rear of the optical section by upstanding shank sections. The iris loops are placed behind the iris, and the shank sections engage an inner edge of the iris to prevent lateral shifting of the lens in the eye so that it can properly focus. The Fedorov et al U.S. Pat. No. 3,673,616 shows schematically how an intraocular lens is attached to the iris.
Because the iris retention loops and shanks are of an extremely small diameter, i.e. 0.005 to 0.010 inch, their circular cross section in the shank area tends to cut into the inner edge of the iris in the same manner as a wire cheese cutter. This is a particular problem when the iris is stretched over the shank sections.